The Dark Light won the Edgar for Best First Novel in 1949, and Bart Spicer went on to write six more novels about p. i. Carney Wilde. In what was a first for a p.i. series (and maybe a last), Spicer's story arc covers Wilde's entire career, from his lowly beginnings, his marriage, and finally his ownership of a big detective agency.
Spicer wasn't hesitatant to deal with racial issues (see also, and especiall, Blues for the Prince). In The Dark Light, Wilde is hired by a deacon in a black church to find his minister, who's disappeared. Almost immediately, people start dying, including the deacon. Spicer was a fine plotter, and the disparate elements that make up the mystery include a diamond earring, a tough cop, and a beautiful woman.
Bart Spicer's been criminally overlooked in the last few decades, but he wrote one of the best p.i. series of the '50s, or for that matter any of the decades afterward. If you like tough but compassionate ops, careful plotting, well-developed characters, and good writing, you owe it to yourself to read Spicer's novel.